The invention relates to a logic element, particularly a bipolar gate circuit, for an LSI-circuit, in which one terminal of a first Schottky-diode is connected, in high-resistance direction, to a first input and one terminal of a second Schottky-diode is connected, in high resistance direction, to a second input, with the remaining terminals of the first and second diodes being connected to one terminal of a first resistance and to the base of a transistor, and the second terminal of the first resistance being connected to a reference potential.
A known, high-speed bipolar gate circuit for LSI-circuits employs different Schottky-diodes which are connected to the base terminal of a pnp-transistor, functioning as the current source, and to the base terminal of a Schottky-transistor (see Electronics, December 1974, pp 36 and 38).
The production of so-called C.sup.3 L-gate circuit (C.sup.3 L = Complementary Constant Current Logic) is difficult as two technologically different Schottky-diode types as well as one pnp-transistor must be employed. As a result of the different Schottky-diode types required, complex manufacturing processes are involved with relatively poor production efficiency. At the same time, the use of a pnp-transistor as current source involves greater demands on all production steps, again reducing the ultimate production efficiency. Further, the pnp-transistor involves an additional capacitance and poor amplification along with large base currents which do not participate in the switch-over operation. As a result, the use of a pnp-transistors is accompanied by a loss in power and switching time.
In order to achieve a high-speed bipolar gate circuit with relatively simple production operations, high packing density, and good amplification, a logic element, particularly a bipolar gate circuit for LSI-circuits, has already been proposed, in which the logic element has at least two Schottky-diodes in a semiconductor member, in which the Schottky-diodes performing different functions have areas of different efficiency and/or variable dopings of the semiconductor member beneath the Schottky contacts, for the purpose of effecting a change in the starting voltages.
In such prior bipolar gate circuit, respective Schottky-diodes are connected at their first terminals, in high-resistance direction, to first and second inputs respectively, with the second terminals of the diodes being connected to one end of a resistance, to the terminal of a third Schottky diode, and to the base of a transistor. The second terminal of the resistance was connected to a reference potential and the second terminal of the third Schottky-diode was connected in common to an output and to the collector of a transistor. The Schottky contacts of the first and second diodes exhibited a different surface area or a variable doping of the semiconductor member beneath the Schottky contacts, as compared with the third Schottky-diode.
Such a logic element, particularly a bipolar gate circuit for LSI-circuits, is achieved, which is relatively simple to produce and which exhibits a rapid switching characteristic, together with a high packing density. The technologically different Schottky-diodes are produced either by the employment of Schottky-diodes in the same technology of metallization, with a low starting voltage and different surface area, or by changing the starting voltage by means of variations in the doping of the semiconductor member, for example by means of ion implantation. In addition, the pnp-transistor in the C.sup.3 L-gate circuit is replaced by a resistance, whereby the switching behavior is even further improved.
In the known C.sup.3 L-gate circuit and the proposed gate circuit, which is also designated as a S.sup.3 TL-gate circuit ( = Small Swing Schottky Logic), experiments have shown that the logic swing, i.e. the differential between the operational levels, is relatively small and consequently, with very limited freedom from interference. In addition, Schottky-diodes, particularly with different starting voltages involve a certain risk in production efficiency.